Mutagenically-derived nontumorigenic strains of Agrobacterium tumefaciens will be genetically analyzed to determine whether relevant mutations lie on plasmid or chromosomal DNA. Genetic techniques will be developed for mapping chromosomal mutations in A. tumefaciens. These techniques will be used to determine position and linkage states of any mutations conferring avirulence which prove to reside on the bacterial chromosome. Mutations involving plasmid DNA will be analyzed by DNA DNA hybridization and restriction endonuclease cleavage. Differences in host range between strains of the A. tumefaciens B6 group will be investigated in terms of plasmid complement. We will look for correlations between presence of muliple plasmids in such strains and their ability to induce tumors on different host plants. If such correlations can be found, genetic techniques will be used to analyze host range dependence on plasmid complement. Lastly, techniques will be developed for analyzing transcriptional and translational products of plasmids from tumorigenic and nontumorigenic strains of A. tumefaciens.